在 Spring Integration 中，RequestHandlerRetryAdvice 无法与 Ftp.outboundGateway 一起使用

我的情况与描述的类似这个问题。区别在于我不使用WebFlux.outboundGateway but an Ftp.outboundGateway我称之为AbstractRemoteFileOutboundGateway.Command.GET命令，常见的问题是我无法获得定义的RequestHandlerRetryAdvice要使用的。

配置如下所示（精简到相关部分）：

@RestController
@RequestMapping( value = "/somepath" )
public class DownloadController
{
   private DownloadGateway downloadGateway;

   public DownloadController( DownloadGateway downloadGateway )
   {
      this.downloadGateway = downloadGateway;
   }

   @PostMapping( "/downloads" )
   public void download( @RequestParam( "filename" ) String filename )
   {
      Map<String, Object> headers = new HashMap<>();

      downloadGateway.triggerDownload( filename, headers );
   }
}    

@MessagingGateway
public interface DownloadGateway
{
   @Gateway( requestChannel = "downloadFiles.input" )
   void triggerDownload( Object value, Map<String, Object> headers );
}

@Configuration
@EnableIntegration
public class FtpDefinition
{
   private FtpProperties ftpProperties;

   public FtpDefinition( FtpProperties ftpProperties )
   {
      this.ftpProperties = ftpProperties;
   }

   @Bean
   public DirectChannel gatewayDownloadsOutputChannel()
   {
      return new DirectChannel();
   }

   @Bean
   public IntegrationFlow downloadFiles( RemoteFileOutboundGatewaySpec<FTPFile, FtpOutboundGatewaySpec> getRemoteFile )
   {
      return f -> f.handle( getRemoteFile, getRetryAdvice() )
                   .channel( "gatewayDownloadsOutputChannel" );
   }

   private Consumer<GenericEndpointSpec<AbstractRemoteFileOutboundGateway<FTPFile>>> getRetryAdvice()
   {
      return e -> e.advice( ( (Supplier<RequestHandlerRetryAdvice>) () -> {
         RequestHandlerRetryAdvice advice = new RequestHandlerRetryAdvice();
         advice.setRetryTemplate( getRetryTemplate() );
         return advice;
      } ).get() );
   }

   private RetryTemplate getRetryTemplate()
   {
      RetryTemplate result = new RetryTemplate();

      FixedBackOffPolicy backOffPolicy = new FixedBackOffPolicy();
      backOffPolicy.setBackOffPeriod( 5000 );

      result.setBackOffPolicy( backOffPolicy );
      return result;
   }

   @Bean
   public RemoteFileOutboundGatewaySpec<FTPFile, FtpOutboundGatewaySpec> getRemoteFile( SessionFactory sessionFactory )
   {
      return 
         Ftp.outboundGateway( sessionFactory,
                              AbstractRemoteFileOutboundGateway.Command.GET,
                              "payload" )
            .fileExistsMode( FileExistsMode.REPLACE )
            .localDirectoryExpression( "'" + ftpProperties.getLocalDir() + "'" )
            .autoCreateLocalDirectory( true );
   }

   @Bean
   public SessionFactory<FTPFile> ftpSessionFactory()
   {
      DefaultFtpSessionFactory sessionFactory = new DefaultFtpSessionFactory();
      sessionFactory.setHost( ftpProperties.getServers().get( 0 ).getHost() );
      sessionFactory.setPort( ftpProperties.getServers().get( 0 ).getPort() );
      sessionFactory.setUsername( ftpProperties.getServers().get( 0 ).getUser() );
      sessionFactory.setPassword( ftpProperties.getServers().get( 0 ).getPassword() );
      return sessionFactory;
   }
}

@SpringBootApplication
@EnableIntegration
@IntegrationComponentScan
public class FtpTestApplication {

    public static void main(String[] args) {
        SpringApplication.run( FtpTestApplication.class, args );
    }
}

@Configuration
@PropertySource( "classpath:ftp.properties" )
@ConfigurationProperties( prefix = "ftp" )
@Data
public class FtpProperties
{
   @NotNull
   private String localDir;

   @NotNull
   private List<Server> servers;

   @Data
   public static class Server
   {
      @NotNull
      private String host;

      @NotNull
      private int port;

      @NotNull
      private String user;

      @NotNull
      private String password;
   }
}

控制器主要只是用于测试目的，在实际实现中有一个轮询器。我的FtpProperties保存服务器列表，因为在实际实现中，我使用DelegatingSessionFactory根据一些参数选择一个实例。

根据加里·拉塞尔的评论，我希望重试失败的下载。但是，如果我中断下载服务器端（通过在 FileZilla 实例中发出“Kick user”），我只会立即获得堆栈跟踪，而无需重试：

org.apache.commons.net.ftp.FTPConnectionClosedException: FTP response 421 received.  Server closed connection.
[...]

我还需要上传文件，为此我使用Ftp.outboundAdapter。在这种情况下并且具有相同的RetryTemplate，如果我中断上传服务器端，Spring Integration 会再执行两次尝试，每次延迟 5 秒，然后才记录java.net.SocketException: Connection reset，一切如预期。

我尝试进行一些调试，并注意到在第一次尝试通过Ftp.outboundAdapter，断点RequestHandlerRetryAdvice.doInvoke()被击中。但通过下载时Ftp.outboundGateway，该断点是never hit.

我的配置有问题吗，谁能帮我解决一下RequestHandlerRetryAdvice跟...共事Ftp.outboundGateway/AbstractRemoteFileOutboundGateway.Command.GET?

抱歉耽搁了;本周我们在 SpringOne 平台。

问题是由于网关规范是一个 bean - 网关最终在应用建议之前被初始化。

我像这样改变了你的代码......

@Bean
public IntegrationFlow downloadFiles(SessionFactory<FTPFile> sessionFactory) {
    return f -> f.handle(getRemoteFile(sessionFactory), getRetryAdvice())
            .channel("gatewayDownloadsOutputChannel");
}

...

private RemoteFileOutboundGatewaySpec<FTPFile, FtpOutboundGatewaySpec> getRemoteFile(SessionFactory<FTPFile> sessionFactory) {
    return Ftp.outboundGateway(sessionFactory,
            AbstractRemoteFileOutboundGateway.Command.GET,
            "payload")
            .fileExistsMode(FileExistsMode.REPLACE)
            .localDirectoryExpression("'/tmp'")
            .autoCreateLocalDirectory(true);
}

...它起作用了。

通常最好不要直接处理规范，而只是将它们内联到流程定义中......

@Bean
public IntegrationFlow downloadFiles(SessionFactory<FTPFile> sessionFactory) {
    return f -> f.handle(Ftp.outboundGateway(sessionFactory,
            AbstractRemoteFileOutboundGateway.Command.GET,
            "payload")
            .fileExistsMode(FileExistsMode.REPLACE)
            .localDirectoryExpression("'/tmp'")
            .autoCreateLocalDirectory(true), getRetryAdvice())
        .channel("gatewayDownloadsOutputChannel");
}